Novel approaches for simulating hot forming and heat treatment

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Utilizing novel concepts, we make detailed simulations of hot forming and heat treatment of metallic materials possible. Our approach links thermomechanical material behavior and microstructure evolution using a comprehensive thermodynamic framework. This allows us to efficiently represent elastic-plastic material behavior, recovery, recrystallization, grain coarsening, texture evolution and precipitation as well as the related hardening and softening processes. Despite the complexity of the material model, parameter identification only requires moderate effort because most parameters have a physical significance and are therefore well known. We develop the theoretical basis of the project within the Priority Program 1713 "Strong Coupling of Thermo-Chemical and Thermo-Mechanical States in Applied Materials" of the German Research Foundation (DFG).

Our material model is suited for application to cold and hot forming processes, heat treatment and combinations of such processes. This enables us to represent a complete process chain without the need to transfer data from one model to another between the sub-steps. The numerically implemented material model can be applied to design, analysis and optimization of process routes, e.g. in hot and cold forming as well as heat treatment. Moreover, a potential application is within on-line process control. At the moment, we are working on an implementation for finite element programs in order to make the model applicable for design and analysis of semi-finished products and complex parts.

Video: Hot compression test in the thermomechanical simulator "Gleeble 3150"

Simulation of grain coarsening during the heat treatment of copper alloys

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In pure copper, the mean grain size increases while the type of grain size distribution remains unchanged.

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In a precipitate hardened copper alloy, grain coarsening is retarded and the characteristics of the grain size distribution change.

Simulated tensile tests of carbon steel at various temperatures and strain rates

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Stress-Strain-Diagram

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Evolution of the mean grain size